1. Field
Embodiments of the present invention relate to large engine systems.
2. Description of Related Art
In diesel fuel powered transportation environments, extremely cold temperatures adversely affect diesel engine operation. Generally, large diesel engines, such as locomotive engines, are not shut down during cold weather conditions due to the difficulty in restarting. Diesel engines do not have the benefit of an electric spark to generate combustion and must rely on heat generated by compressing air to ignite fuel in the engine cylinders.
In low temperature conditions (ambient temperatures below about 40° F.), various factors contribute to the difficulty in starting a diesel engine. First, cold ambient air drawn into the engine must be increased in temperature sufficiently to cause combustion. Second, diesel fuel tends to exhibit poor viscous qualities at low temperatures. Furthermore, engine oil that provides lubrication for an engine is most effective within specific temperature limits, generally corresponding to normal operating temperature of the engine. When cold, the engine lube-oil tends to impede engine starting. Moreover, most engines require a large electrical supply, typically provided by a battery, in order to turn over and start the engine. Batteries are also adversely affected by severe cold weather.
In cold weather, large engines are typically idled overnight to avoid the need to restart in the morning and to provide heat to the crew space. Locomotives that must operate in extremely cold environmental conditions must be run continuously, at high fuel cost, or, when shut down, must be drained of engine coolant and provided with supplemental electrical service and heaters, also at high cost. To avoid engine damage, locomotives typically include a dump valve that activates if the engine coolant comes close to freezing by dumping all of the engine coolant. If a locomotive dumps its main engine coolant, a tank car or tank truck must replenish the coolant prior to restarting of the locomotive, creating delays and increased costs.
In warm weather, locomotive engines typically idle to provide air conditioning and other services, including lighting, air pressure, and power to electrical appliances. If a locomotive is shut down, solid-state static inverters that transform dc power from the locomotive batteries to useful ac power can provide electrical power for air conditioning and other services. Devices such as inverters are parasitic loads that tend to drain the batteries, which may adversely affect engine reliability. Alternatively, wayside electrical power can be supplied, but such power generally does not maintain air conditioning.
Long term idling of large diesel engines results in additional deleterious effects. For example, large diesel engines are susceptible to “wet stacking” due to piston ring leakage caused by idling for long periods of time in cold weather. Moreover, long term idling is economically inefficient, resulting in primary engine wear, and high fuel and lube-oil consumption, for example.
Several systems have attempted to maintain warmth in a large diesel engine under low temperature ambient conditions. For example, U.S. Pat. No. 4,424,775 discloses an auxiliary engine for maintaining the coolant, lube-oil, and batteries of a primary diesel engine in restarting condition by using the heat of the auxiliary engine exhaust to keep coolant, lube-oil, and batteries sufficiently warm. U.S. Pat. No. 4,762,170 discloses a system for facilitating the restarting of a truck diesel engine in cold weather by maintaining the fuel, coolant, and lube-oil warm through interconnected fluid systems. U.S. Pat. No. 4,711,204 discloses a small diesel engine for providing heat to the coolant of a primary diesel engine in cold weather. The small engine drives a centrifugal pump with restricted flow such that the coolant is heated and then pumped through the primary cooling lines in reverse flow. In such systems, an electrical generator or inverter may be included to maintain a charge for the batteries.
U.S. Pat. No. 5,072,703 discloses an apparatus for restarting a truck diesel engine to maintain a comfortable sleeper compartment temperature. Inputs require that the truck be parked prior to restarting the engine. U.S. Pat. No. 4,577,599 discloses a remote starter for an internal combustion engine that adjusts fuel and air input to the engine based upon engine speed and temperature.